Minimal Callback Not Used

[Gary Beene]

Trivial comment: Even though I like minimal code, I do this ...

CallBack Function DlgProc() As Long
   Select Case Cb.Msg
      Case %WM_Command
         Select Case Cb.Ctl
            Case %IDC_DoThis : DoThis
         End Select
   End Select
End Function

... instead of this, even when the code is for a quick test using throwaway code.

CallBack Function DlgProc() As Long
   If Cb.Msg = %WM_Command And Cb.Ctl = %IDC_DoThis Then DoThis
End Function

[Frank Rogers]

I don't see anything wrong with it as long as you don't care which message is coming from control %IDC_DoThis. Could be a click or a hover or ...

You could make it

If (Cb.Msg = %WM_Command) And (Cb.Ctl = %IDC_DoThis) And (Cb.CtlMsg = %BN_Clicked) Then DoThis

but you would need a line for each message and each control.

[Dale Yarker]

Agree.

IF/THEN is just as legit a test as SELECT CASE.

It depends on how many messages, controls and sub-messages need testing.

For one CB.MSG (like %WM_COMMAND) and multiple controls I might use an IF THEN/END IF with a SELECT CASE nested inside it.

Even for a complicated callback, it is possible to use only nested IF THEN/ ELSEIFs/END IFs. It would just be "ugly" to read compared to nested SELECT CASEs; but the tests of the values would be valid (no coding errors of course!)

There is no magic saying callbacks must use SELECT CASE. SELECT CASE just often is easier to write and read/modify later.

Cheers,

[Stuart McLachlan]

Me too. It's clear and easily expandable.

And since that structure is automagically created for me when I select "New File As... " and pick "DDT-SImple Dlg" off my list of 10 templates, it's actually less work that writing one or more multi-conditional IF statements.

2
CCWIN
.bas
[PBWIN]DDT-Simple Dlg

#COMPILE EXE
#DIM ALL
ENUM ctrls SINGULAR
    IDC_btnQuit = 1001
END ENUM

FUNCTION PBMAIN() AS LONG
   LOCAL lRslt AS LONG
   LOCAL hDlg  AS DWORD

    DIALOG NEW 0, "DDT SHell", , , 200, 180, %WS_SYSMENU, TO hDlg
    CONTROL ADD BUTTON , hDlg,%IDC_btnQuit,"Quit",60,130,80,20
    DIALOG SHOW MODAL hDlg, CALL MainDlgCB TO lRslt
END FUNCTION

CALLBACK FUNCTION MainDlgCB()
    SELECT CASE AS LONG CB.MSG
        CASE %WM_INITDIALOG

        CASE %WM_NCACTIVATE

        CASE %WM_COMMAND
            SELECT CASE AS LONG CB.CTL
                CASE %IDC_btnQUIT
                    IF CB.CTLMSG = %BN_CLICKED OR CB.CTLMSG = 1 THEN
                        DIALOG END CBHNDL
                    END IF
            END SELECT
    END SELECT
END FUNCTION

[Michael Mattias]

Please note "SELECT CASE AS LONG" is NOT the same test as "IF/ELSE" if you are testing a 32-bit integer with PowerBASIC code.

SELECT CASE AS LONG tests all 32 bits,(unsigned) and IF/ELSE tests 31 bits plus a sign bit.

e.g., using SELECT CASE AS AS LONG , -1& = &FFFFFFFF but that is not true using IF/ELSE

I mention this because the code example in post #4 uses SELECT CASE AS LONG.